Monolithic Power Systems Inc. MP3398BGF

Overview

MP3398BGF from Monolithic Power Systems is a 4-string white LED step-up controller with analog and PWM dimming support, designed for large LCD panel backlighting. It delivers up to 350mA per string, achieves ±2.5% current matching across strings, operates from 5V–28V input, and drives external N-MOSFETs to generate boosted output voltages up to 55V for WLED arrays in desktop monitors and 2D/3D TVs.

For engineers reviewing the MP3398BGF datasheet, MP3398BGF pinout, MP3398BGF application, or MP3398BGF equivalent, this device requires attention to its dual-dimming interface (PWM/ADIM), programmable switching frequency (100–500 kHz), OVP resistor-divider configuration, cascading capability via ISENSE, and thermal shutdown recovery behavior.

Technical Context

The MP3398BGF implements peak-current-mode control with fixed-frequency oscillator programmable via OSC pin resistor (e.g., 374kΩ → 180kHz). Its internal 6V LDO (VCC) powers gate driver and logic, while four matched current sinks regulate LED strings independently with 800mV compliance voltage at 330mA.

It integrates open/short LED protection triggered by LEDX pin voltage thresholds (e.g., <196mV for open, >6.3V for short), latch-off overcurrent protection at 640mV on ISENSE, and recoverable thermal shutdown at 150°C with 25°C hysteresis - all operating without external supervision.

Key Specifications

Pinout & Package

TSSOP16-EP package with exposed pad thermally connected to GND - provides low θJA (45°C/W) for high-power LED driving in compact layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar white LED backlight controller applications.

Compared with MP3398AGF, the MP3398BGF adds cascading capability and tighter current matching; versus RT9701GSP, it offers greater string count, dimming flexibility, and programmable frequency - making it optimal for mid-to-large panel backlight systems requiring scalability and precision.

Availability

MP3398BGF is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, 2D/3D LCD TVs, and commercial video signage requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.

Supply support for MP3398BGF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with design centers in the US, China, and Taiwan.

The MP3398BGF belongs to MPS's WLED backlight controller product line, engineered specifically for energy-efficient, high-reliability LCD panel illumination in consumer and commercial displays.

FAQ

What is the minimum recommended ISET resistor value for MP3398BGF?

The ISET pin regulates at 1.225V; using R_ISET = 1.225V / I_LED, the minimum practical resistor is ~3.5kΩ for 350mA per string. Lower values risk exceeding internal current limits and violating absolute max ratings on ISET pin current.

Can MP3398BGF drive LEDs with forward voltage above 28V per string?

Yes - the boost output can reach up to 55V (per ABSOLUTE MAXIMUM RATINGS), allowing series strings of 10+ white LEDs (V_F ≈ 3.2V each). The IC automatically selects the highest LEDX voltage to regulate the bus, ensuring all strings receive sufficient headroom.

How does the MP3398BGF handle an open LED string during operation?

When an LED string opens, its corresponding LEDX pin drops below 196mV. After >4μs at this level, the IC marks that string as faulty, disables its current sink, and continues regulating remaining strings using the highest active LEDX voltage - preserving partial backlight functionality.

Is the OSC pin voltage fixed, and how does it affect frequency accuracy?

Yes - the OSC pin is internally regulated to 1.23V ±30mV. Frequency accuracy depends on ROSC resistor tolerance and temperature coefficient; using 1% metal-film resistors yields ±5% typical switching frequency variation over temperature and process.

What happens if both PWM and ADIM pins are driven simultaneously?

The MP3398BGF applies multiplicative dimming: final LED current = I_set × D_PWM × D_ADIM. This enables fine-grained brightness control - e.g., coarse adjustment via ADIM and micro-adjustment via PWM - without hardware modification.

Does the TSSOP16-EP package require special PCB layout considerations for thermal performance?

Yes - the exposed pad must be soldered to a solid copper thermal pad (≥200 mm²) connected to internal/external GND planes via ≥4 thermal vias (0.3mm diameter). Failure to do so risks exceeding 125°C junction temperature at full load, triggering thermal shutdown.

Can MP3398BGF operate without an external MOSFET?

No - it is a controller-only IC. An external N-channel MOSFET is mandatory for the boost switch; the GATE pin drives its gate. No internal power switch is integrated, distinguishing it from fully integrated LED drivers like MP3302.